<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta name="viewport" content="width=device-width">
  <title>JS Bin</title>
  <!--  引入umd的React-->
  <script src="https://cdn.bootcdn.net/ajax/libs/react/17.0.0-rc.0/umd/react.production.min.js"></script>
  <!--  引入umd的React-dom-->
  <script
    src="https://cdn.bootcdn.net/ajax/libs/react-dom/0.0.0-0c756fb-f7f79fd/umd/react-dom.production.min.js"></script>
</head>
<body>
<div id="root"></div>
</body>